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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthornick1c
    • CommentTimeAug 24th 2020
    We live in West Cornwall within a few miles of the sea in almost every direction. This generally gives us mild winters and cooler summers, which is great. It also means that the RH rarely falls below 80%. Our granite barn has been lime pointed, painted with Beek BS+ & had new DG windows fitted. Mould is still a problem, I believe condensation is the main issue in the cooler months and the high absolute level of water in the atmosphere in the summer. Much though I would like to rip out the inside, fit breathable insulation & plaster in lime it is not financially viable/ possible, in any case it would not help in the summer.
    What is the best way of managing this? We have used a dehumidifier in the past (ebac) but found it difficult to get a balance - at one point the doors warped! Are there more sophisticated units that would give a decent level of control, or would fitting a humidistat with a plug attached for the ebac do the job?
    The problem is likely to become more significant as our parents may well move in this winter.
    • CommentTimeAug 25th 2020
    I would start by buying a few cheap humidity/temperature meters and logging what they indicate in various places around the house. (Or an electronic logging system if you prefer and want to spend the cash.) Just to double-check what the reality is. Having several of the same type means you can check their readings against each other.

    Apart from a dehumidifier, the other main thing to look at is ventilation. Even in summer, it's usually cooler at night so even outside air at 100% humidity contains less water than what may be inside. Opening windows wide for an hour or two can help a lot. Fly screens are very useful! An MVHR system is likely to help.

    My only experience of high humidity in a house was a Victorian place we rented for a while. Mould in corners, mouldy carpets under anything resting on the floor. So floor and wall surfaces must be left clear, so that air can circulate across them.

    Others probably know a lot more than me.
    We've been using a dehumidifier for about 3 years, but the house is getting damper. I'm slowly replacing the modern plasterboard with lime plaster and breathable insulation. It does stop the damp in that area but seems to make it worse in the places I have yet to do (most of the house!)

    I bought a MHRV system that I'll be fitting once my current project is completed. I have high hopes that this will perform much better than the dehumidifier as it extracts from all of the 'wet rooms' rather than the immediate area in which it is located. Maybe this could be an option?
    • CommentAuthortony
    • CommentTimeAug 25th 2020
    Guaranteed solution is MVHR — idiots solution is PIV, expensive as you pay to run the input fan which effectively blows your heat out of the house costing a lot more than the fan energy , it will work but is not green.
    • CommentAuthortony
    • CommentTimeAug 25th 2020
    Re Humidity, I agree that you need reading, my sensors were a couple of quid each and run on batteries.

    Do you really mean damp mould and condensation or high humidity?
    • CommentTimeAug 25th 2020
    Posted By: tonyidiots solution is PIV

    You're right it's an idiots' solution - anybody who uses it is an idiot.

    PIV famously tends to force air to be pushed out through cracks etc and INCREASE the probability of interstitial condensation. Exactly what you don't want in a high-humidity environment. MEV or dMEV would be a saner suggestion, since they pull air in through cracks to a warmer place where condensation won't happen, and exhaust in through defined place(s) where it can be controlled.
    • CommentAuthornick1c
    • CommentTimeAug 25th 2020
    Does anyone have recommendations for meters? It does seem the obvious place to start...
    MVHR isn’t practical as rather is nowhere to run the ducts, we have a vaulted ceiling upstairs & there is virtually no space between the ground & first floors.
    Were it possible I can see it helping in the winter due to the inside/outside temperature differentials - but in summer where it is often 18+deg & 80%+RH outside surely the RH inside would still be high.
    Do any dehumidifiers come with accurate meters in them?
    • CommentAuthorLF
    • CommentTimeAug 25th 2020
    Meters seem to change frequently on amazon mine is no longer there. They are not expensive. Use reviews to guide.

    Where is water coming from ? Stop it /minimise it
    Do you dry washing in the house ? If you need to do it in one room with window open or with dehumidifier on
    Are showers near extraction fans to get moisture out of the house ?
    Is damp coming into the house through plumbing leaks, bad gutters or something else ?

    Open windows and get moisture out and cooler drier air in.

    I use simple mechanical humidistat without numbers on dehumidifiers and use local meter near by to check it is in correct ball park. It seems fine.
    • CommentAuthorSteveZ
    • CommentTimeAug 25th 2020
    +1 on Cornwall! It is a lot wetter than most people think.

    I have had several of these handy little monitors for a few years. They are accurate enough to give you a guide, and if you leave them all close together until they have stable readings, you can mark up the individual differences, if any. This should give you more confidence in their readings when they are placed elsewhere.

    Check for Temperature and humidity meters on the well-known websites, and you will find offers for 5 off for around £12. For a little more they can have max/min functions - up to you! Mine are labelled HTC-1 and are still available
    • CommentAuthorLF
    • CommentTimeAug 28th 2020
    We have not really answered your question about 80% RH, 18 C in summer. If inside t 21 C this is about 60%
    Some good Cornish content in this tread.
    "How does mechanical ventilation keep the humidity lower than the outside air it brings in?"
    An intelligent extractor fan(with or without heat recovery) that operates when internal rh is moderately high but only when outside is much drier? Seal up house when warm and wet outside ...
    Just tried a wireless data logging one with display and claimed 1 year Battery life. Stacks up with my meter in bathroom. The app is great can see trends and export data. Seems brilliant!
    • CommentTimeAug 28th 2020
    I am very happy with a couple of cheap RH% (and temp) meters that we bought years ago and are still available on Amazon with a slightly different product code:


    I do also use my (product name omitted!) smart TRVs in every room to capture and log RH% every few minutes:



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